<HTML><HEAD><TITLE>Alpine Technical Notes:  Behind the Scenes</TITLE></HEAD><BODY>
<H1>Behind the Scenes</H1>

Many people ask how certain <EM>Alpine</EM> features are implemented.  This section 
outlines some of the details. 

<H2><A NAME="addrbook">Address Books</A></H2>

There are two types of address book storage. There
are <EM>local</EM> address books, which are the address books that are
stored in a local file; and there
are <EM>remote</EM> address books, which are stored on an IMAP server.

<H4><A NAME="remote-abooks">Information About Remote Address Books</A></H4>

<BLOCKQUOTE>
NOTE: The remote address book capability does not allow you to access an
existing local address book from a remote system! That is, you can't set
the remote address book to something like <CODE>{remote.host}.addressbook</CODE>
and expect to access the existing <CODE>.addressbook</CODE> <EM>file</EM>
on remote.host. Instead, you need to create a new remote address book in
a new, previously unused remote mail <EM>folder</EM>. Then you can use the
<EM>Select</EM> and <EM>Apply Save</EM> commands in the address book screen to
<EM>Save</EM> all of the entries from an existing local address book to
the new remote address book.
</BLOCKQUOTE>
<P>

A remote address book is stored in a mail folder on an
IMAP server.
An <EM>Alpine</EM> remote address book is just like an <EM>Alpine</EM> local address book
in that it is not interoperable with other email clients.
The folder is a regular folder containing mail messages but
those messages are special. The first message must be an alpine remote
address book header message which contains the header <EM>x-pine-addrbook</EM>.
The last message in the folder contains the address book data.
In between the first
and the last message are old versions of the address book data. The address
book data is simply stored in the message as it would be on disk, with no MIME
encoding. When it is used the data from the last message in the folder is
copied to a local file and then that file is used exactly like a local
address book file is used. When a change is made the modified local file
is appended to the remote folder in a new message. In other words, the
local file is just a cache copy of the data in the remote folder. Each client
which uses the remote address book will have its own cache copy of the data.
Whenever a copy is done the entire address book is copied, not just the
entries which have changed.
<P>

<EM>Alpine</EM> can tell that the remote data has changed
by one of several methods.
If the date contained in the Date header of the last message has changed then
it knows it has changed. If the UID of the last message has changed, or the
number of messages in the folder has changed, it knows that it has changed.
When <EM>Alpine</EM> discovers the folder has changed it gets
a new copy and puts it in the local cache file.
<P>

There is a configuration file variable for remote address books called
<A HREF="config.html#remote-abook-metafile"><EM>remote-abook-metafile</EM></A>.
The variable is the name of a file in which
information about remote address books is stored. There is one line in the
metafile for each remote address book. The information stored there is the
name of the cache file and information to help figure out when the remote
folder was last changed. If the metafile or any of the cache files is deleted
then <EM>Alpine</EM> will rebuild them the next time it runs.
<P>

Remote address books have names that look just like regular
<A HREF="config-notes.html#remote-folders">remote mail folder</A> names.
For example:

<BLOCKQUOTE>
          {host.domain}foldername<BR>
</BLOCKQUOTE>

<EM>Alpine</EM> decides whether or not an address book is remote simply by
looking at the first character of the address book name and comparing
it to '{'.

<H4>Information About All Address Books</H4>

The address book is named, by default, <CODE>.addressbook</CODE> in the
user's Unix home directory, or in the case of <EM>PC-Alpine</EM>,
<CODE>ADDRBOOK</CODE>, in the same directory as the <CODE>PINERC</CODE> file.
There may be more than
one address book, and the default name can be overridden via an entry in
any of the <EM>Alpine</EM> configuration files. The two configuration variables
<A HREF="config.html#pers-abook"><EM>address-book</EM></A>
and <A HREF="config.html#glob-abook"><EM>global-address-book</EM></A>
are used to specify the names of the address books.
Each of these variables is a list
variable. The total set of address books for a user is the combination of
all the address books specified in these two lists. Each entry in the
list is an optional nickname followed by an address book name. The nickname is
everything up to the last space before the file name. The
<EM>global-address-book</EM> list will typically be configured in the
system-wide configuration file, though a user may override it like most
other variables. Address books which are listed in the
<EM>global-address-book</EM> variable are forced read-only, and are
typically shared among multiple users. <P>

Local address books (or local cache files for remote address books) are
simple text files with lines in the format: 

<BLOCKQUOTE>
          &lt;nickname&gt;TAB&lt;fullname&gt;TAB&lt;address&gt;TAB&lt;fcc&gt;TAB&lt;comments&gt;<BR>
</BLOCKQUOTE>

The last two fields are optional. A "line" may be made up of multiple
actual lines in the file by using continuation lines, which are lines
beginning with SPACE characters. The line breaks may be after TABs or in
between addresses in a distribution list.
Each <EM>actual</EM> line in the file must
be less than 1000 characters in length.
<P>

Nicknames (the first field) are short names that the user types instead of
typing in the full address. There are several characters which aren't
allowed in nicknames in order to avoid ambiguity when parsing the address
(SPACE, COMMA, @, ", ;, :, (, ), [, ], <, >, \).
Nicknames aren't required. In fact,
none of the fields is required. <P>

The <EM>fullname</EM> field is usually stored as Last_name, First_name, in order
that a sort on the fullname field comes out sorted by Last_name.
If there is an unquoted comma in the fullname,
<EM>Alpine</EM> will flip the first and last name around and get rid of
the comma when using the entry in a composition. It isn't required that
there be a comma, that's only useful if the user wants the entries to sort
on last names. <P>

The <EM>address</EM> field takes one
of two forms, depending on whether the entry
is a single (simple) address or a distribution list. For a simple entry,
the address field is an RFC 2822 address. This could be either the
email-address part of the address, i.e., the part that goes inside the
brackets (&lt;&gt;), or it could be a full RFC 2822 address. The phrase part
of the address (the fullname) is used unless there is a fullname present
in the fullname field of the address book entry. In that case, the fullname
of the address book entry replaces the fullname of the address. For a
distribution list, the &lt;address&gt; is in the format: 

<BLOCKQUOTE>
          "(" &lt;address&gt;, &lt;address&gt;, &lt;address&gt;, ... ")"<BR>
</BLOCKQUOTE>
<P>

The only purpose for the parentheses around the list of addresses is to
make it easier for the parsing routines to tell that it is a simple entry
instead of a list. The two are displayed differently and treated slightly
differently in some cases, though most of the distinction has disappeared.
Each of the addresses in a list can be a full RFC 2822 address with
fullname included, or it may be just the simple email-address part of the
address. This allows the user to have a list which includes the fullnames
of all the list members. In both the simple and list cases,
addresses may also be other nicknames which appear in this address book or
in one of the other address books. (Those nicknames are searched for by
looking through the address books in the order they appear in the address
book screen, with the first match winning.) Lists may be nested. If
addresses refer to each other in a loop (for example, list A includes
list B which includes list A again) this is detected and flagged. In that
case, the address will be changed to "**** address loop ****". <P>

The optional <EM>fcc</EM> field is a folder name, just like the fcc field in the
composer headers. If the first address in the To field of a composition
comes from an address book entry with an fcc field, then that fcc is
placed in the fcc header in the composer. <P>

The <EM>comments</EM> field is just a free
text field for storing comments about an
entry. By default, neither the fcc nor the comments field is shown on the
screen in the address book screen. You may make those fields visible by
configuring the variable
<A HREF="config.html#abook-formats"><EM>addressbook-formats</EM></A>.
They are also searched when you use the <EM>WhereIs</EM>
command in the address book screen and are visible when you
<EM>View</EM> or <EM>Update</EM> an entry. <P>

The address book is displayed in the order that it is stored. 
When the user chooses a different sorting criterion, the data is actually
sorted and stored, as opposed to showing a sorted view of the data. <P>

When the address book is written out, it is first written to a temporary
file and if that write is successful it is renamed. This guards
against errors writing the file that might destroy the whole address book. 
The address book is re-written after each change. If the address book
is a remote address book, the file is then appended to the remote mail
folder using IMAP. <P>

The end-of-line character(s) in the address book file are those native to
the system writing it. So it is &lt;LF&gt; on Unix and
&lt;CR&gt;&lt;LF&gt; on PC's. However, both Unix and PC versions of <EM>Alpine</EM>
can read either format, so it should be possible to share a read-only
address book among the two populations (using NFS, for example).
<P>

<HR>

<H3><A NAME="addrbook-lu">Address Book Lookup File</A></H3>

<EM>Pine</EM> used an additional file for each address book, called
the LookUp file. It had the same name as the address book file
with the suffix ".lu" appended.
<EM>Alpine</EM> no longer uses a lookup file.
<P>

<H4>Validity Checking of Address Books</H4>

There is no file locking done on <EM>Alpine</EM> address books, however, there
is considerable validity checking done to make sure that the address book
hasn't changed unexpectedly. Whenever the address book is about to be changed,
a check is made to see if the file is newer than when we read it or the
remote address book folder has changed since we last copied it. If either
of these is true, the change is aborted.
<P>

There is an automatic, behind-the-scene check that happens every so often,
also. For example, if someone else changes one of the address books that
you have configured, your <EM>Alpine</EM>'s copy of the address book will usually
be updated automatically without you noticing. This checking happens at the
same time as new mail checking takes place, unless you are actively using
the address book, in which case it happens more frequently.
<P>

<HR>

<H2><A NAME="remote-config">Remote Configuration</A></H2>

Configuration information may be stored remotely.
Remote configuration information is stored in a folder on an IMAP server.
This should be a folder which is used only for storing the configuration
information.
In other words, it should be a folder which didn't exist before.
<P>
Remote configuration folders are very similar to remote address book folders.
They both consist of a header message, which serves to identify the type
of folder; the last message, which contains the data; and intermediate
messages, which contain old versions of the data.
The first message must contain the header <EM>x-pine-pinerc</EM>.
<P>
When a remote configuration is being used, the folder is checked to make
sure it is a remote configuration folder, then the data contained in the
last message is copied to a temporary file.
That file is treated just like any regular local configuration file from
that point on.
Whenever a configuration change is made, the entire file is copied back
to the IMAP server and is appended to the folder as a new message.
<P>
Because remote configuration folders are so similar to remote address books,
the configuration variable
<A HREF="config.html#remote-abook-metafile"><EM>remote-abook-metafile</EM></A>
is used by both.
<P>
Remote configuration folders have names that look just like regular
<A HREF="config-notes.html#remote-folders">remote mail folder</A> names.
For example:

<BLOCKQUOTE>
          {host.domain}mypinerc<BR>
</BLOCKQUOTE>

<EM>Alpine</EM> decides whether or not a configuration file is remote simply by
looking at the first character of the name and comparing
it to '{'.
<P>

<HR>

<H2><A NAME="checkpoint">Checkpointing</A></H2>

Periodically <EM>Alpine</EM> will save the whole
mail folder to disk to prevent loss
of any mail or mail status in the case that it gets interrupted,
disconnected, or crashes.  The period of time <EM>Alpine</EM> waits to do the
checkpoint is calculated to be minimally intrusive.  The timing can be
changed (but usually isn't) at compile time.  Folder checkpointing happens
for both local folders and those being accessed with IMAP.  The delays are
divided into three categories:  <P>

<BLOCKQUOTE>
The exact algorithm given below is no longer correct.
It has gotten more complicated over time.
However, this gives the general idea <EM>Alpine</EM> uses
when deciding whether or not to do a checkpoint.
</BLOCKQUOTE>

<DL COMPACT>

<DT> Good Time:

<DD> This occurs when <EM>Alpine</EM> has been idle for more than 30 seconds.  In
this case <EM>Alpine</EM> will checkpoint if 12 changes
to the file have been made or
at least one change has been made and a checkpoint hasn't been done for
five minutes.  <P>

<DT> Bad Time:

<DD> This occurs just after <EM>Alpine</EM> has
executed some command.  <EM>Alpine</EM> will
checkpoint if there are 36 outstanding changes to the mail file or at
least one change and no checkpoint for ten minutes.  <P>

<DT> Very Bad Time:

<DD> Done when composing a message.  In this case, <EM>Alpine</EM> will only
checkpoint if at least 48 changes have been made or at least one change has been
made in the last twenty minutes with no checkpoint.  <P>

</DL>

<HR>

<H2><A NAME="debug">Debug Files</A></H2>

If UNIX <EM>Alpine</EM> is compiled with the compiler
<EM>DEBUG</EM> option on (the default),
then <EM>Alpine</EM> will produce debugging output to a file.
This can be disabled at compile-time with the --disable-debug configure option,
or at run-time with the command line flag -d0.
The file is
normally <CODE>.pine-debugX</CODE> in the user's home directory where
<EM>X</EM> goes from 1 to 4.  Number 1 is always the most recent session
and 4 the oldest.  Four are saved because often the user has gone in and
out of <EM>Alpine</EM> a few times after a problem has occurred before the expert
actually gets to look at it.  The amount of output in the debug files
varies with the debug level set when <EM>Alpine</EM> is
compiled and/or as a command
line flag.  The default is level 2.  This shows very general things and
records errors.  Level 9 produces copious amounts of output for each
keystroke.  <P>

Similarly, <EM>PC-Alpine</EM> creates debug files
named <CODE>pinedebg.txtX</CODE> in the
same directory as the <CODE>PINERC</CODE> file.  <P>

<HR>

<H2><A NAME="INBOX">INBOX and Special Folders</A></H2>

The <EM>INBOX</EM> folder is treated specially.  It is normally kept open
constantly so that the arrival of new mail can be detected.  The name
<EM>INBOX</EM> refers to wherever new mail is retrieved on the system.  If
the <A HREF="config.html#inbox-path"><EM>inbox-path</EM></A> variable is set,
then <EM>INBOX</EM> refers to
that.  IMAP servers understand the concept of <EM>INBOX</EM>, so
specifying the folder <EM>{imap.u.example.edu}INBOX</EM> is meaningful. 
The case of the word <EM>INBOX</EM> is not important,
but <EM>Alpine</EM> tends to display it in all capital letters.  <P>

The folders for <A HREF="config.html#def-fcc">sent mail</A>
and <A HREF="config.html#def-save">saved messages</A> folders are
also somewhat special.
They are automatically created if they are absent and recreated
if they are deleted.  <P>

<HR>

<H2><A NAME="help">Internal Help Files</A></H2>

The file <CODE>pine.hlp</CODE> in the <CODE>alpine</CODE> subdirectory of the
distribution contains all the help text for <EM>Alpine</EM>.
It is compiled right into the <EM>Alpine</EM> binary as strings.
This is done to simplify installation and configuration.
The <CODE>pine.hlp</CODE> file is in a
special format that is documented at the beginning of the file.
It is divided into sections, each with a name that winds up being referenced as
a global variable.  This file is processed during the build process and
turned into a C file that is compiled into <EM>Alpine</EM>.  <P>

<HR>

<H2><A NAME="char-set">International Character Sets</A></H2>

<EM>Alpine</EM> uses Unicode characters internally and 
it is a goal for <EM>Alpine</EM> to handle email in many different languages.
<EM>Alpine</EM> will properly display only left-to-right character sets
in a fixed-width font. Specifically, <EM>Alpine</EM> assumes that a fixed-width
font is in use, in the sense that
characters are assumed to take up zero, one, or two character cell
widths from left to right on the screen. This is true even in <EM>PC-Alpine</EM>.
<P>

<EM>Alpine</EM> recognizes some local character sets which are right-to-left
(Arabic, Hebrew, and Thai) or not representable in a fixed-width font
(Arabic) and properly converts texts in these character sets to/from
Unicode; however, there are known display bugs with these character
sets.
<P>

There are three possible configuration character settings and some
environment variable settings which can affect how <EM>Alpine</EM>
handles international characters.
The first two of these are only available in UNIX <EM>Alpine</EM>.
The three configuration options are
<EM>display-character-set</EM>,
<EM>keyboard-character-set</EM>, and
<EM>posting-character-set</EM>.
The <EM>keyboard-character-set</EM> defaults to being the same value
as the <EM>display-character-set</EM>, and that is usually correct, because
the keyboard almost always produces characters in the same character set
as the display displays.
The <EM>display-character-set</EM> is the character set that <EM>Alpine</EM>
will attempt to use when sending characters to the display.
<P>
Besides those variables there is also
<A HREF="config.html#use-system-translation"><EM>use-system-translation</EM></A>
which can be used instead of these.
That usage is only lightly tested and is not recommended.
<P>

By default, the <EM>display-character-set</EM> variable is not set and UNIX <EM>Alpine</EM>
will attempt to get this information from the environment.
In particular, the <CODE>nl_langinfo(CODESET)</CODE> call is used.
This usually depends on the setting of the environment variables LANG or LC_CTYPE.
An explicit configuration setting for <EM>display-character-set</EM> will,
of course, override any default setting.
<P>
For <EM>PC-Alpine</EM> the <EM>display-character-set</EM>
and the <EM>keyboard-character-set</EM>
are always equivalent to <CODE>UTF-8</CODE> and this is not settable.
<P>

It is probably best to use UNIX <EM>Alpine</EM> in a terminal emulator
capable of displaying UTF-8 characters, since that will allow you to
view just about any received text that is correctly formatted (note,
however, the above comments about known index display bugs with certain
character sets). You'll need to have an emulator which uses a UTF-8 font
and you'll need to set up your environment to use a UTF-8 charmap. For
example, on a Linux system you might include
<P>
<CENTER> <CODE>setenv LANG en_US.UTF-8</CODE> </CENTER>
<P>

or something similar in your UNIX startup files.
You'd also have to select a UTF-8 font in your terminal emulator.
<P>

The types of values that the character set variables may be set to are
<CODE>UTF-8</CODE>, <CODE>ISO-8859-1</CODE>, or <CODE>EUC-JP</CODE>.
The <CODE>ISO-2022</CODE> character sets are not supported for input or
for display, but as a special case, <CODE>ISO-2022-JP</CODE> is supported
for use only as a <EM>posting-character-set</EM>.
In the Setup/Config screen you may choose from a list of all the
character sets <EM>Alpine</EM> knows about by using the &quot;T&quot; ToCharsets command.
Here is a list of many of the possible character sets:

<P>
<TABLE>
<TR> <TD>UTF-8</TD> <TD>Unicode</TD> </TR>
<TR> <TD>US-ASCII</TD> <TD>7 bit American English characters</TD> </TR>
<TR> <TD>ISO-8859-1</TD> <TD>8 bit European "Latin 1" character set</TD> </TR>
<TR> <TD>ISO-8859-2</TD> <TD>8 bit European "Latin 2" character set</TD> </TR>
<TR> <TD>ISO-8859-3</TD> <TD>8 bit European "Latin 3" character set</TD> </TR>
<TR> <TD>ISO-8859-4</TD> <TD>8 bit European "Latin 4" character set</TD> </TR>
<TR> <TD>ISO-8859-5</TD> <TD>8 bit Latin and Cyrillic</TD> </TR>
<TR> <TD>ISO-8859-6</TD> <TD>8 bit Latin and Arabic</TD> </TR>
<TR> <TD>ISO-8859-7</TD> <TD>8 bit Latin and Greek</TD> </TR>
<TR> <TD>ISO-8859-8</TD> <TD>8 bit Latin and Hebrew</TD> </TR>
<TR> <TD>ISO-8859-9</TD> <TD>8 bit European "Latin 5" character set</TD> </TR>
<TR> <TD>ISO-8859-10</TD> <TD>8 bit European "Latin 6" character set</TD> </TR>
<TR> <TD>ISO-8859-11</TD> <TD>Latin and Thai</TD> </TR>
<TR> <TD>ISO-8859-12</TD> <TD>Reserved</TD> </TR>
<TR> <TD>ISO-8859-13</TD> <TD>8 bit European "Latin 7" character set</TD> </TR>
<TR> <TD>ISO-8859-14</TD> <TD>8 bit European "Latin 8" character set</TD> </TR>
<TR> <TD>ISO-8859-15</TD> <TD>8 bit European "Latin 9" character set</TD> </TR>
<TR> <TD>ISO-8859-16</TD> <TD>8 bit European "Latin 10" character set</TD> </TR>
<TR> <TD>KOI8-R</TD> <TD>8 bit Latin and Russian</TD> </TR>
<TR> <TD>KOI8-U</TD> <TD>8 bit Latin and Ukrainian</TD> </TR>
<TR> <TD>WINDOWS-1251</TD> <TD>8 bit Latin and Russian</TD> </TR>
<TR> <TD>TIS-620</TD> <TD>8 bit Latin and Thai</TD> </TR>
<TR> <TD>VISCII</TD> <TD>8 bit Latin and Vietnamese</TD> </TR>
<TR> <TD>GBK</TD> <TD>Latin and Chinese Simplified</TD> </TR>
<TR> <TD>GB2312</TD> <TD>Latin and Chinese Simplified</TD> </TR>
<TR> <TD>CN-GB</TD> <TD>Latin and Chinese Simplified</TD> </TR>
<TR> <TD>BIG5</TD> <TD>Latin and Chinese Traditional</TD> </TR>
<TR> <TD>BIG-5</TD> <TD>Latin and Chinese Traditional</TD> </TR>
<TR> <TD>EUC-JP</TD> <TD>Latin and Japanese</TD> </TR>
<TR> <TD>SHIFT-JIS</TD> <TD>Latin and Japanese</TD> </TR>
<TR> <TD>EUC-KR</TD> <TD>Latin and Korean</TD> </TR>
<TR> <TD>KSC5601</TD> <TD>Latin and Korean</TD> </TR>
</TABLE>
<P>

When reading incoming email, <EM>Alpine</EM> understands many different
character sets and is able to convert the incoming mail into Unicode.
The Unicode will be converted to the <EM>display-character-set</EM>
for display on your terminal.
Characters typed at the keyboard will be converted from the
<EM>keyboard-character-set</EM> to Unicode for <EM>Alpine</EM>'s internal
use.
You may find that you can read some malformed messages that do not
contain a character set label by setting the option
<A HREF="config.html#unknown-character-set"><EM>unknown-character-set</EM></A>.
<P>

The <EM>posting-character-set</EM> is used when sending messages.
The default behavior obtained by leaving this variable unset is usually
what is wanted. In that default case, <EM>Alpine</EM> will attempt
to label the message with the most specific character set from the
rather arbitrary set
<P>
US-ASCII, ISO-8859-15,
ISO-8859-1, ISO-8859-2, VISCII, KOI8-R, KOI8-U, ISO-8859-7, ISO-8859-6,
ISO-8859-8, TIS-620, ISO-2022-JP, GB2312, BIG5, EUC-KR, and UTF-8.
<P>

For example, if the message is made up of only US-ASCII characters, it
will be labeled US-ASCII. Otherwise, if it is all ISO-8859-15 characters,
that will be the label. If that doesn't work the same is tried for the
remaining members of the list.

<P>
It might make sense to set <EM>posting-character-set</EM> to an
explicit value instead.
For example, if you usually send messages in Greek, setting this
option to ISO-8859-7 will result in messages being labeled as
US-ASCII if there are no non-ascii characters, ISO-8859-7 if there
are only Greek characters, or UTF-8 if there are some characters
which aren't representable in ISO-8859-7.
Another possibility is to set this option explicitly to UTF-8.
In that case
<EM>Alpine</EM> labels only ascii messages as US-ASCII and all other
messages as UTF-8.
<P>

<HR>

<H2><A NAME="interrupt">Interrupted and Postponed Messages</A></H2>

If the user is composing mail and is interrupted by being disconnected
(SIGHUP, SIGTERM or end of file on the standard input), <EM>Alpine</EM> will save the
interrupted composition and allow the user to continue it when he or she
resumes <EM>Alpine</EM>.  As the next <EM>Alpine</EM> session starts, a message will be given
that an interrupted message can be continued.  To continue the interrupted
message, simply go into the composer.  To get rid of the interrupted
message, go into the composer and then cancel the message with
<EM>^C.</EM> <P>

Composition of half-done messages may be postponed to a later time by
giving the <EM>^O</EM> command.  Other messages can be composed while
postponed messages wait.  All of the postponed messages are kept in a
single folder.  Postponing is a good way to quickly reference other
messages while composing.  <P>

<HR>

<H2><A NAME="status">Message Status</A></H2>

The c-client library allows for several flags or status marks to be set
for each message.  <EM>Alpine</EM> uses four of these flags:  UNSEEN, DELETED,
ANSWERED, and FLAGGED.  The <CODE>N</CODE> in <EM>Alpine</EM>'s
FOLDER INDEX means that a
message is unseen-it has not been read from this folder yet.  The <CODE>D</CODE>
means that a message is marked for deletion.
Messages marked with <CODE>D</CODE> are
removed when the user <EM>Expunges</EM> the folder (which usually happens
when the folder is closed or the user quits <EM>Alpine</EM>).
The <CODE>A</CODE> in <EM>Alpine</EM>'s
FOLDER INDEX means that the message has been replied-to.  The <CODE>*</CODE> in
<EM>Alpine</EM>'s FOLDER INDEX means that the message has been ``flagged'' as
important.  That is, the user used the <EM>Flag</EM> command to turn the
FLAGGED flag on.  This flag can mean whatever the user wants it to mean. 
It is just a way to mark some messages as being different from others.  It
will usually probably be used to mark a message as somehow being
``important''. For Berkeley format folders, the message status is written
into the email folder itself on the header lines marked <CODE>Status:</CODE>
and <CODE>X-Status</CODE>.
<P>
It is also possible for a user to define their own flags in addition to the
standard system flags above.
In <EM>Alpine</EM> these user defined flags are called Keywords.
<P>

<HR>

<H2><A NAME="MIME-read">MIME:  Reading a Message</A></H2>

<EM>Alpine</EM> should be able to handle just about any MIME message.  When a MIME
message is received, <EM>Alpine</EM> will display a list of all the parts, their
types and sizes.  It will display the attachments when possible and
appropriate and allow users to <EM>Save</EM> all other attachments.  <P>

<EM>Alpine</EM> honors the "mailcap"
configuration system for specifying external programs for handling attachments.
The mailcap file maps MIME attachment types to the external programs
loaded on your system which can display and/or print the file.
A sample mailcap file
comes bundled with the <EM>Alpine</EM> distribution.  It includes comments which
explain the syntax you need to use for mailcap.  With the mailcap file,
any program (mail readers, newsreaders, WWW clients) can use the same
configuration for handling MIME-encoded data.  <P>

If a <CODE>MAILCAPS</CODE> environment variable is defined,
<EM>Alpine</EM> will use that to look
for one or more mailcap files, which are combined.  In the absence of
<CODE>MAILCAPS</CODE>, Unix <EM>Alpine</EM> will look for
a personal mailcap file in <CODE>~/.mailcap</CODE>
and combine that with a system-wide file in <CODE>/etc/mailcap</CODE>.
<EM>PC-Alpine</EM> will look for a file named <CODE>MAILCAP</CODE> in the
same directory as the <CODE>PINERC</CODE> file,
and/or the directory containing the <CODE>ALPINE.EXE</CODE> executable.  <P>

Messages which include <EM>rich text</EM> or <EM>enriched text</EM> in the
main body will be displayed in a very limited way (it will show bold and
underlining).  <P>

If <EM>Alpine</EM> sees a MIME message part tagged as type IMAGE,
and <EM>Alpine</EM>'s
<A HREF="config.html#image-viewer"><EM>image-viewer</EM></A>
configuration variable is set, <EM>Alpine</EM> will attempt to
send that attachment to the named image viewing program.  In the case of
UNIX <EM>Alpine</EM>, the <CODE>DISPLAY</CODE> environment variable is
checked to see if an X-terminal is being used (which can handle the images).
If the <EM>image-viewer</EM> variable is not set,
<EM>Alpine</EM> uses the <EM>mailcap</EM>
system to determine what to do with IMAGE types, just as it does for any
other non-TEXT type, e.g. type APPLICATION.  For MIME's generic "catch
all" type, APPLICATION/OCTET-STREAM, the <EM>mailcap</EM> file will
probably not specify any action, but <EM>Alpine</EM> users may always
<EM>Save</EM> any MIME attachment to a file.  <P>

MIME type "text/plain" is handled a little bit differently than the
other types.  If you are viewing the main body part in the MESSAGE TEXT
viewing screen, then <EM>Alpine</EM> will use its internal viewer to display it.
This happens even if there is a mailcap description which matches this
particular type.
However, if you view a part of
type "text/plain" from the ATTACHMENT INDEX screen, then <EM>Alpine</EM> will check
the mailcap database for a matching entry and use it in preference to
its internal viewer.  <P>

Some text attachments, specifically those which are just other email messages
forwarded as MIME messages, are displayed as part of the main body of the
message.  This distinction allows easy display when possible (the forward
as MIME case) and use of an attachment viewer when that is desirable (the
plain text file attachment case).  <P>

If the parts of a multipart message are alternate versions of the same
thing <EM>Alpine</EM> will select and display the one best suited.
For parts of type "message/external-body", the parameters showing the
retrieval method will be displayed, and the retrieval process is automated.
Messages of type "message/partial" are not supported.  <P>

<HR>

<H2><A NAME="MIME-send">MIME:  Sending a Message</A></H2>

There are two important factors when trying to include an attachment in a
message:  encoding and labeling.
<EM>Alpine</EM> has rules for both of these which
try to assure that the message goes out in a form that is robust and can
be handled by other MIME mail readers.  <P>

MIME has two ways of encoding data-Quoted-Printable and Base64. 
Quoted-Printable leaves the ASCII text alone and only changes 8-bit
characters to "=" followed by the hex digits.  For example, "=09" is a
tab.  It has the advantage that it is mostly readable and that it allows
for end of line conversions between unlike systems.  Base64 encoding is
similar to <EM>uuencode</EM> or <EM>btoa</EM> and just encodes a raw bit
stream.  This encoding is designed to get text and binary files through
even the most improperly implemented and configured gateways intact, even
those that distort uuencoded data.  <P>

<STRONG>All</STRONG> attachments are encoded using Base64 encoding.  This
is so that the attachment will arrive at the other end looking exactly
like it did when it was sent.  Since Base64 is completely unreadable
except by MIME-capable mailers or programs, there is an obvious tradeoff
being made here.  We chose to ensure absolutely reliable transport of
attachments at the cost of requiring a MIME-capable mailer to read them. 
If the user doesn't want absolute integrity he or she may always
<EM>include</EM> text (with the <EM>^R</EM> command) in the body of a
message instead of attaching it.  With this policy, the only time
quoted-printable encoding is used is when the main body of a message
includes special foreign language characters.  <P>

When an attachment is to be sent, <EM>Alpine</EM> sniffs through it to try to set the
right label (content-type and subtype).  An attachment with any lines
longer than 500 characters in it or more than 10% of the characters are
8-bit it will be considered binary data.  <EM>Alpine</EM> will recognize (and
correctly label) a few special types including GIF, JPEG, PostScript, and
some audio formats. Another method which can be more robust and flexible for
determining the content-type and subtype is to base it on the file extension.
This method uses a <A HREF="config-notes.html#mime.types">MIME.Types File</A>.
<P>

If it is not binary data (has only a small proportion of 8-bit characters
in it,) the attachment is considered 8-bit text.  8-bit text attachments
are labeled "text/plain" with charset set to the value of the user's
<EM>keyboard-character-set</EM> variable.  If an attachment is ASCII (no 8-bit
characters) and contains no control characters
then it is considered plain ASCII text.  Such attachments are given the MIME label
"text/plain;  charset=US-ASCII", regardless of the setting of the user's
<EM>keyboard-character-set</EM> variable.  <P>

All other attachments are unrecognized and therefore given the generic
MIME label "application/octet-stream".  <P>

<HR>

<H2><A NAME="new-mail">New Mail Notification</A></H2>

<EM>Alpine</EM> checks for new mail in the <EM>INBOX</EM> and in
the currently open folder every two and a half minutes by default.
This default can be changed in the system-wide configuration file or
at compile-time with the --with-mailcheck-interval=VALUE configuration
option.
A user can change it by changing the option
<A HREF="config.html#mail-check"><EM>mail-check-interval</EM></A>.
A new mail check can be manually forced by redrawing the screen with a <EM>^L</EM>.  <P>

When there is new mail, the message(s) will appear in the index, the
screen will beep, and a notice showing the sender and subject will be
displayed.  If there has been more than one new message since you last
issued a command to <EM>Alpine</EM>, the notice will show the count of new messages
and the sender of the most recent one.  <P>

<HR>

<H2><A NAME="NFS">NFS</A></H2>

It is possible to access mail folders on <EM>NFS</EM> mounted volumes with
<EM>Alpine</EM>, but there are some drawbacks to doing this, especially in the case
of incoming-message folders that may be concurrently updated by <EM>Alpine</EM> and
the system's mail delivery agent.  One concern is that <EM>Alpine</EM>'s
user-contention locks don't work because <EM>/tmp</EM> is usually not
shared, and even if it was, <EM>flock()</EM> doesn't work across
<EM>NFS.</EM> <P> The implementation of the standard UNIX ".lock" file
locking has been modified to work with <EM>NFS</EM> as follows.  Standard
hitching post locking is used so first a uniquely named file is created,
usually something like <EM>xxxx.host.time.pid.</EM> Then a link to it is
created named <EM>xxxx.lock</EM> where the folder being locked is
<EM>xxxx.</EM> This file constitutes the lock.  This is a standard UNIX
locking scheme.  After the link returns, a <EM>stat(2)</EM> is done on the
file.  If the file has two links, it is concluded that the lock succeeded
and it is safe to proceed.  <P>

In order to minimize the risks of locking failures via <EM>NFS</EM>, we strongly
recommend using IMAP rather than <EM>NFS</EM> to access remote incoming message
folders, e.g. your <EM>INBOX</EM>.  However, it is generally safe to access
personal saved-message folders via <EM>NFS</EM> since it is unlikely that
more than one process will be updating those folders at any given time. 
Still, some problems may occur when two <EM>Alpine</EM> sessions try to access the
same mail folder from different hosts without using IMAP.  Imagine the
scenario:  <EM>Alpine</EM>-A performs a write that changes the folder.  <EM>Alpine</EM>-B then
attempts to perform a write on the same folder.  <EM>Alpine</EM>-B will get upset
that the file has been changed from underneath it and abort operations on
the folder.  <EM>Alpine</EM>-B will continue to display mail from the folder that it
has in its internal cache, but it will not read or write any further data. 
The only thing that will be lost out of the <EM>Alpine</EM>-B session when this
happens is the last few status changes.  <P>

If other mail readers besides <EM>Alpine</EM> are involved, all bets are off. 
Typically, mailers don't take any precautions against a user opening a
mailbox more than once and no special precautions are taken to prevent
<EM>NFS</EM> problems.  <P>

<HR>

<H2><A NAME="print">Printers and Printing</A></H2>

UNIX <EM>Alpine</EM> can print to the standard UNIX line printers or to generic
printers attached to ANSI terminals using the escape sequences to turn the
printer on and off.  The user has a choice of three printers in the
configuration.  <P>

The first setting, <EM>attached-to-ansi</EM>, makes use of escape
sequences on ANSI/VT100 terminals.  It uses "&lt;ESC&gt;[5i" to begin
directing all output sent to the terminal to the printer and then
"&lt;ESC&gt;[4i" to return to normal.  <EM>Alpine</EM> will send these escape
sequences if the printer is set to <EM>attached-to-ansi.</EM> This works
with most ANSI/VT100 emulators on Macs and PCs such as kermit, NCSA
telnet, VersaTerm Pro, and WinQVT.  Various terminal emulators implement
the print feature differently.
There is also a closely
related method called <EM>attached-to-ansi-no-formfeed</EM> which is
the same except for the lack of formfeed character at the end of the
print job.
<P>
<EM>Attached-to-wyse</EM> and <EM>attached-to-wyse-no-formfeed</EM> are
very similar to "attached-to-ansi".
The only difference is in the control characters sent to turn the printer
on and off.
The Wyse version uses Ctrl-R for on, and Ctrl-T for off.
<P>

The second selection is the standard UNIX print command.  The default is
<EM>lpr</EM>, but it can be changed on a system basis to anything so
desired in <CODE>/usr/local/lib/pine.conf</CODE>. <P>

The third selection is
the user's personal choice for a UNIX print command.  The text to be
printed is piped into the command.  <EM>Enscript</EM> or <EM>lpr</EM> with
options are popular choices.  The actual command is retained even if one
of the other print selections is used for a while.  <P>

Both the second and third sections are actually lists of possible commands
rather than single commands. <P>

If you have a PostScript printer attached to a PC or Macintosh, then you
will need to use a utility called <EM>ansiprt</EM> to get printouts on
your printer.  <EM>Ansiprt</EM> source code and details can be found in
the <CODE>./contrib</CODE> directory of the <EM>Alpine</EM> distribution.  <P>

<HR>

<H2><A NAME="save">Save and Export</A></H2>

<EM>Alpine</EM> users get two options for moving
messages in <EM>Alpine</EM>: <EM>Save</EM> and <EM>Export</EM>.
<EM>Save</EM> is used when the message should remain ``in the
<EM>Alpine</EM> realm.'' Saved messages include the complete header
(including header lines normally hidden by <EM>Alpine</EM>),
are placed in a <EM>Alpine</EM> folder collection and
accumulate in a standard folder format which <EM>Alpine</EM> can read.
In contrast, the <EM>Export</EM> command is used to write the contents
of a message to a file for use outside of <EM>Alpine</EM>.
Messages which have been exported are
placed in the user's home directory (unless the feature
<A HREF="config.html#use-current-dir"><EM>use-current-dir</EM></A> is
turned on), not in a <EM>Alpine</EM> folder collection. 
Unless FullHeaderMode is toggled on, all delivery-oriented headers are
stripped from the message.  Even with <EM>Export</EM>, <EM>Alpine</EM> retains
message separators so that multiple messages can accumulate in a single
file and subsequently be accessed as a folder.  On UNIX systems, the
<EM>Export</EM> command pays attention to the standard <EM>umask</EM> for
the setting of the file permissions.  <P>

<HR>

<H2><A NAME="sent-mail">Sent Mail</A></H2>

<EM>Alpine</EM>'s default behavior is to keep a copy of each outgoing message in a
special "sent mail" folder.  This folder is also called the fcc for "file
carbon copy".  The existence, location and name of the sent mail folder
are all configurable.  Sent mail archiving can be turned off by setting
the configuration variable
<A HREF="config.html#def-fcc"><EM>default-fcc=""</EM></A>.  The sent mail folder
is assumed to be in the default collection for <EM>Save</EM>s,
which is the first collection named in
<A HREF="config.html#fold-coll"><EM>folder-collections</EM></A>.
The name of the folder
can be chosen by entering a name in <EM>default-fcc</EM>.
With <EM>PC-Alpine</EM>,
this can be a bit complicated.  If the default collection for <EM>Save</EM>s is
local (DOS), then the <EM>default-fcc</EM> needs to be <CODE>SENTMAIL</CODE>,
which is syntax for a DOS file.  However, if the default collection
for <EM>Save</EM>s is
remote, then the <EM>default-fcc</EM> needs to be <CODE>sent-mail</CODE>
to match the UNIX syntax.  <P>

The configuration variable
<A HREF="config.html#fcc-name-rule"><EM>fcc-name-rule</EM></A>
also plays a role in selecting the folder to save sent mail in. <P>

A danger here is that the sent mail could grow without bound.  For this
reason, we thought it useful to encourage the users to periodically prune
their sent mail folder.  The first time <EM>Alpine</EM> is used each month it will
offer to archive all messages sent from the month before.  <EM>Alpine</EM> also
offers to delete all the sent mail archive folders which are more than 1
month old.  If the user or system has disabled sent mail archiving (by
setting the configuration variable <EM>default-fcc=""</EM>)
there will be no pruning question. 
<P>

<HR>

<H2><A NAME="spell">Spell Checker</A></H2>

Both UNIX <EM>Alpine</EM> and <EM>PC-Alpine</EM>
depend on the system for their spell checking and dictionary.  <EM>Pico</EM>, the
text editor, uses the same spell checking scheme as <EM>Alpine</EM>.  <P>

Lines beginning with "&gt;" (usually messages included in replies) are not
checked.  The message text to be checked is on the standard input and the
incorrect words are expected on the standard output.  <P>

The default spell checker is UNIX <EM>spell</EM>.  You can replace this
by setting the <A HREF="config.html#speller"><EM>speller</EM></A> configuration
variable.
A common choice for a superior replacement is <EM>ispell</EM>.

<P>
<EM>PC-Alpine</EM> relies on the aspell library being installed.
Aspell is independent of Alpine.  The Windows version has
traditionally been available at
<A HREF="http://aspell.net/win32/">http://aspell.net/win32/</A>.  You'll
need to download and install both Aspell and a precompiled dictionary.
Aspell is provided in an installer package.  Dictionaries, to be
installed after Aspell, are in '.exe' files to download and run.
<P>

<HR>

<H2><A NAME="terminal">Terminal Emulation and Key Mapping</A></H2>

UNIX <EM>Alpine</EM> has been designed to require as little as possible from the terminal. 
At the minimum, <EM>Alpine</EM> requires cursor positioning, clear to end of line,
and inverse video.  Unfortunately, there are terminals that are missing
some of these such as a vt52.  <EM>Alpine</EM> makes no assumptions as to whether the
terminal wraps or doesn't wrap.  If the terminal has other capabilities it
may use some of them.  <EM>Alpine</EM> won't run well on older terminals that require
a space on the screen to change video attributes, such as the Televideo
925.  One can get around this on some terminals by using "protected field"
mode.  The terminal can be made to go into protected mode for reverse
video, and then reverse video is assigned to protected mode.  <P>

<EM>Alpine</EM> handles screens of most any size and resizing on the fly.  It catches
SIGWINCH and does the appropriate thing.
<P>

On the input side of things, <EM>Alpine</EM> uses all the standard keys, most of the
control keys and (in function-key mode) the function keys.  <EM>Alpine</EM> avoids
certain control keys, specifically ^S, ^Q, ^H, and <EM>^\</EM>
because they have other meanings outside of <EM>Alpine</EM> (they control data flow,
etc.) <EM>^H</EM> is treated the same as the <EM>delete</EM> key, so the
<EM>backspace</EM> or <EM>delete</EM> keys always work regardless of any
configuration.  There is a feature <EM>compose-maps-delete-key-to-ctrl-d</EM>
which makes the delete key behave like ^D rather than ^H (deletes current
character instead of previous character).  <P>

Sometimes a communications program or communications server in between you
and the other end will eat certain control characters.  There is a
work-around when you need it.  If you type two escape characters followed
by a character that will be interpreted as the character with the control
key depressed.  For example, <EM>ESC ESC T</EM> is equivalent to
<EM>^T</EM>.  <P>

When a function key is pressed and <EM>Alpine</EM> is in regular (non-function key)
mode, <EM>Alpine</EM> traps escape sequences for a number of common function keys so
users don't get an error message or have an unexpected command executed
for each character in the function key's escape sequence.  <EM>Alpine</EM> expects
the following escape sequences from terminals defined as VT100:  <P>

<BLOCKQUOTE>
        ANSI/VT100<BR>
F1:     &lt;ESC&gt;OP <BR>
F2:     &lt;ESC&gt;OQ <BR>
F3:     &lt;ESC&gt;OR <BR>
F4:     &lt;ESC&gt;OS <BR>
F5:     &lt;ESC&gt;Op <BR>
F6:     &lt;ESC&gt;Oq <BR>
F7:     &lt;ESC&gt;Or <BR>
F8:     &lt;ESC&gt;Os <BR>
F9:     &lt;ESC&gt;Ot <BR>
F10:    &lt;ESC&gt;Ou <BR>
F11:    &lt;ESC&gt;Ov <BR>
</BLOCKQUOTE>
<P>

Arrow keys are a special case.  <EM>Alpine</EM> has the escape sequences for a number
of conventions for arrow keys hard coded and does not use <EM>termcap</EM>
to discover them.  This is because <EM>termcap</EM> is sometimes
incorrect, and because many users have PC's running terminal emulators
that don't conform exactly to what they claim to emulate.
There is a feature called
<A HREF="config.html#termdef-takes-precedence"><EM>termdef-takes-precedence</EM></A>
which can be set to cause the <EM>termcap</EM>
or <EM>terminfo</EM> definitions to be used instead of the built in definitions.
Some arrow keys on old terminals send single control characters
like <EM>^K</EM> (one even sends <EM>^\</EM>).
These arrow keys will not work with <EM>Alpine</EM>.
The most popular escape sequences for arrow keys are:  <P>

<BLOCKQUOTE>
Up:	&lt;ESC&gt;[A	&lt;ESC&gt;?x	&lt;ESC&gt;A	&lt;ESC&gt;OA<BR>
Down:	&lt;ESC&gt;[B	&lt;ESC&gt;?r	&lt;ESC&gt;B	&lt;ESC&gt;OB<BR>
Right:	&lt;ESC&gt;[C	&lt;ESC&gt;?v	&lt;ESC&gt;C	&lt;ESC&gt;OC<BR>
Left:	&lt;ESC&gt;[D	&lt;ESC&gt;?t	&lt;ESC&gt;D	&lt;ESC&gt;OD<BR>
</BLOCKQUOTE>
<P>

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